Aqueous binder for inorganic-fiber heat-insulating sound-absorbing member, and inorganic-fiber heat-insulating sound-absorbing member

ABSTRACT

Disclosed is an aqueous binder for an inorganic-fiber heat-insulating sound-absorbing member, comprising a polycarboxylic acid and a crosslinking agent for the polycarboxylic acid, in which the polycarboxylic acid comprises a polycarboxylic acid having a weight average molecular weight of 1000 to 20000 and an acid value of 500 to 900 mgKOH/g; the crosslinking agent at least comprises a polyamine without a hydroxyl group, the polyamine having at least one of an amino group and an imino group and having a weight average molecular weight of 100 to 500 and an amine value of 1150 to 1650 mgKOH/g, and a polyol without an amino group and an imino group, the polyol having a hydroxyl group and having a weight average molecular weight of 90 to 250 and an alcohol valence of 3 or more; the ratio of the total mole of the hydroxyl group, amino group and imino group in the crosslinking agent relative to the mole of the carboxy group in the polycarboxylic acid is 0.3 to 1.2; and the ratio of the total mole of the amino group and imino group in the crosslinking agent relative to the total mole of the hydroxyl group, amino group and imino group in the crosslinking agent is 0.01 to 0.2.

TECHNICAL FIELD

The present invention relates to an aqueous binder for an inorganic-fiber heat-insulating sound-absorbing member and an inorganic-fiber heat-insulating sound-absorbing member.

BACKGROUND

Inorganic-fiber heat-insulating sound-absorbing members such as glass wool and rock wool are generally produced by applying a binder to an inorganic fiber and curing the binder. As the binder, a phenol resin and an aqueous binder are known, and the binders described in Patent Literature 1 (Japanese Unexamined Patent Publication No. 2013-117083) are known as the latter one.

SUMMARY

When a phenol resin is used as a binder, there is a risk of generating formaldehyde during and after curing, and a formaldehyde-free binder is frequently desired for reducing an environmental burden.

As to the aqueous binder, a formaldehyde-free aqueous binder is known; however, if a thick inorganic-fiber heat-insulating sound-absorbing member is produced in order to enhance heat insulating performance, the surface part of the inorganic-fiber heat-insulating sound-absorbing member results in serving as a heat insulating layer, with the result that heating at the center portion of the inorganic-fiber heat-insulating sound-absorbing member tends to be insufficient. As a result, the curing degree of the binder at the center portion of the inorganic-fiber heat-insulating sound-absorbing member becomes insufficient. Because of this, a problem that the quality of the inorganic-fiber heat-insulating sound-absorbing members finally obtained varies is raised. Although some methods are known for evaluating the quality of inorganic-fiber heat-insulating sound-absorbing members, the present inventors were aware of a cotton-like shape of the inorganic-fiber heat-insulating sound-absorbing member and found that the peel strength thereof is effectively used as an measure for evaluation as a method for evaluating the quality of inorganic-fiber heat-insulating sound-absorbing members.

In the circumstances, an object of the present invention is to provide an aqueous binder generating no formaldehyde in a curing step and providing excellent peel strength to the inorganic-fiber heat-insulating sound-absorbing member after curing, and provide an inorganic-fiber heat-insulating sound-absorbing member using the aqueous binder.

The present invention provides an aqueous binder for an inorganic-fiber heat-insulating sound-absorbing member, comprising a polycarboxylic acid and a crosslinking agent for the polycarboxylic acid, in which (1) the polycarboxylic acid comprises a polycarboxylic acid having a weight average molecular weight of 1000 to 20000 and an acid value of 500 to 900 mgKOH/g, (2) the crosslinking agent comprises at least one of a reactive compound having only at least one of an amino group and an imino group as a functional group reactive with the polycarboxylic acid or only a hydroxyl group, (3) the reactive compound comprises a polyamine having a weight average molecular weight of 100 to 500 and an amine value of 1150 to 1650 mgKOH/g and a polyol having a weight average molecular weight of 90 to 250 and an alcohol valence of 3 or more, (4) the ratio of the total mole of the hydroxyl group, amino group and imino group in the crosslinking agent relative to the mole of the carboxy group in the polycarboxylic acid is 0.3 to 1.2, and (5) the ratio of the total mole of the amino group and imino group in the crosslinking agent relative to the total mole of the hydroxyl group, amino group and imino group in the crosslinking agent is 0.01 to 0.2.

Since the aqueous binder of the present invention comprises a polycarboxylic acid and a crosslinking agent and has characteristics of (1) to (5) as mentioned above, the aqueous binder is cured without generating formaldehyde in a curing step, with the result that an inorganic-fiber heat-insulating sound-absorbing member excellent in peel strength can be produced.

To describe more specifically, the aqueous binder of the present invention is cured by the reaction between a polycarboxylic acid and a curing agent as mentioned above and thus the reaction proceeds without releasing formaldehyde during thermal curing, with the result that an environmental load in view of e.g., exhaust gas, can be reduced. Since a reactive compound, which comprises a polyamine and a polyol as mentioned above as essential contents, is comprised as a crosslinking agent, a crosslinking reaction sufficiently proceeds in the entire inorganic-fiber heat-insulating sound-absorbing member and excellent peel strength is obtained. Furthermore, since the mole of a functional group capable of reacting with a carboxy group in the crosslinking agent relative to the mole of the carboxy group is specified to fall within the aforementioned range, the polycarboxylic acid and the crosslinking agent can be reacted in just proportion, with the result that a rigid cured product of the aqueous binder can be obtained and physical properties of the inorganic-fiber heat-insulating sound-absorbing member are improved. Moreover, since the mole of an amino group and an imino group relative to the total mole of the hydroxyl group, amino group and imino group in the crosslinking agent is specified to fall within the above range, curing of the aqueous binder proceeds at a high rate, with the result that an inorganic-fiber heat-insulating sound-absorbing member having excellent characteristics can be produced without increasing the temperature of a curing oven and increasing the time for a curing step.

A large number of formaldehyde-free binders have a composition for forming an ester bond in thermal curing. In the esterification reaction, since condensation proceeds while removing water, the reaction rate is low. For the reason, it is necessary to enhance the curing degree of the binder, for example, by increasing the temperature during curing and/or increasing the heating time. Because of this, a decrease in productivity and economic efficiency are problems. In the meantime, a thermosetting binder, in which an amino group and/or an imino group and a carboxy group are reacted (e.g., Patent Literature 1), is also proposed. However, since the hydrophilicity of an amide group or an imide group produced after curing is high, the binder of the resultant inorganic-fiber heat-insulating sound-absorbing member significantly deteriorates due to humidity and bulge of the inorganic-fiber heat-insulating sound-absorbing member due to humidity is sometimes produced. Because of this, quality variation tends to occur. The aqueous binder of the present invention has overcome these drawbacks and is particularly useful in producing inorganic-fiber heat-insulating sound-absorbing members.

It is preferable that the polycarboxylic acid is that comprising as a monomer unit an ethylenically unsaturated monomer having a carboxy group. Since a polycarboxylic acid obtained by polymerizing the ethylenically unsaturated monomer having a carboxy group is used, the amount of carboxy group per molecule can be increased. Also, since a suitable chain transfer agent is used in combination, the weight average molecular weight can be easily controlled. Accordingly, the function as an aqueous binder can be improved by using such a polycarboxylic acid (e.g., crosslinking efficiency and crosslink density are improved due to a large number of carboxy group per molecule); at the same time, variation in performance can be reduced.

It is preferable that the polyol is a sugar alcohol having 3 to 8 carbon atoms in order to further increase the crosslink density of the aqueous binder and further improve the strength of a cured product of the aqueous binder.

It is preferable that the polyamine is an aliphatic polyamine having an alkylene polyamine skeleton. Such a polyamine has excellent water solubility and rarely produces precipitates of e.g., insoluble components, with the result that uniformity of the entire aqueous binder increases. If such a polyamine is used for producing an inorganic-fiber heat-insulating sound-absorbing member, variation in crosslink density from place to place can be prevented and the peel strength becomes excellent.

The aqueous binder can comprise at least one agent selected from the group consisting of a curing accelerator, a silane coupling agent, a dust-inhibiting agent, a neutralizing agent and a colorant. If such a material is added, performance of the aqueous binder can be adjusted in accordance with a curing step and materials to be used (e.g., inorganic fibers), with the result that a composition suitable for final use can be obtained.

If such an aqueous binder is used, an inorganic-fiber heat-insulating sound-absorbing member improved in peel strength can be obtained. More specifically, an inorganic-fiber heat-insulating sound-absorbing member having an inorganic fiber and a cured product of the aqueous binder fixing the inorganic fiber is provided.

The inorganic-fiber heat-insulating sound-absorbing member is free from dimensional change in thickness of a heat insulating material involved in heat-insulating sound-absorbing performance and free from deterioration of rigidity involved in self-standing during construction, even if environmental conditions such as temperature or humidity change, and has physical properties equivalent or superior to the members using a conventional phenolic binder. Thus the inorganic-fiber heat-insulating sound-absorbing member can be suitably used as a core material for a heat-insulating material, a sound-absorbing material or a vacuum insulating material for houses and buildings.

According to the present invention, it is possible to provide an aqueous binder generating no formaldehyde in a curing step and providing excellent peel strength to the inorganic-fiber heat-insulating sound-absorbing member after curing; and provide an inorganic-fiber heat-insulating sound-absorbing member using the aqueous binder.

DETAILED DESCRIPTION

Now, a preferred embodiment of the present invention will be described below. However, the present invention is not particularly limited to the embodiment.

The aqueous binder for an inorganic-fiber heat-insulating sound-absorbing member according to the embodiment (hereinafter sometimes simply referred to as “aqueous binder”) comprises a polycarboxylic acid. As the polycarboxylic acid, a polycarboxylic acid having a weight average molecular weight of 1000 to 20000 and an acid value of 500 to 900 mgKOH/g (hereinafter referred to as “high molecular weight polycarboxylic acid”) is comprised as an essential component. Note that, the weight average molecular weight is a value in terms of polystylene measured by gel permeation chromatography (GPC); and the acid value refers to milligrams (mgKOH) of potassium hydroxide required for neutralizing 1 g of polycarboxylic acid.

As the polycarboxylic acid, it is not excluded to comprise a polycarboxylic acid other than the high molecular weight polycarboxylic acid (for example, a polycarboxylic acid having a weight average molecular weight outside the range of 1000 to 20000 or a polycarboxylic acid having an acid value outside the range of 500 to 900 mgKOH/g); however, the content of the high molecular weight polycarboxylic acid in the whole amount of polycarboxylic acids is preferably 90 mass % or more, further preferably 95 mass % or more and may be 100 mass %.

It is preferable that the high molecular weight polycarboxylic acid is a polymer comprising as a monomer unit an ethylenically unsaturated monomer having a carboxy group, more specifically, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a carboxy group. Note that ethylenically unsaturated monomers having a carboxy group can be used singly or in combination of two or more. The monomer units constituting the high molecular weight polycarboxylic acid include a case consisting of only an ethylenically unsaturated monomer having a carboxy group and a case consisting of an ethylenically unsaturated monomer having a carboxy group and a copolymerization monomer having no carboxy group. In the latter case, the content of the ethylenically unsaturated monomer having a carboxy group based on the total amount of monomers is preferably 90 mass % or more and further preferably 95 mass % or more.

Examples of the ethylenically unsaturated monomer having a carboxy group include (meth)acrylic acid, crotonic acid, fumaric acid, maleic acid, 2-methylmaleic acid, itaconic acid, 2-methylitaconic acid, α-β-methyleneglutaric acid, monoalkyl maleate, monoalkyl fumarate, maleic anhydride, acrylic anhydride, β-(meth)acryloyloxyethylene hydrogen phthalate, β-(meth)acryloyloxyethylene hydrogen maleate and β-(meth)acryloyloxyethylene hydrogen succinate. Of these, (meth)acrylic acid is preferably used since the molecular weight of polycarboxylic acid is easily controlled, and acrylic acid is particularly preferable. In the case where the acid value of the polycarboxylic acid is controlled to be 700 mgKOH/g or more, maleic acid or fumaric acid is preferably used. Note that, “(meth)acryl” means acryl or methacryl and the same applies to analogous compounds.

Examples of the copolymerization monomer having no carboxy group include acrylic monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, normal-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cetyl (meth)acrylate, normal stearyl (meth)acrylate, diethylene glycol ethoxy (meth)acrylate, methyl-3-methoxy (meth)acrylate, ethyl-3-methoxy (meth)acrylate, butyl-3-methoxy (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, tetrahydrofurfuryl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, trihydric or more polyol mono(meth)acrylate, an aminoalkyl (meth)acrylate, a N-alkylaminoalkyl (meth)acrylate and a N,N-dialkylaminoalkyl (meth)acrylate; vinyl monomers such as a vinyl alkyl ether, a N-alkyl vinyl amine, a N,N-dialkyl vinyl amine, N-vinylpyridine, N-vinylimidazole and a N-(alkyl)aminoalkyl vinyl amine; amide monomers such as a (meth)acrylamide, N-alkyl (meth)acrylamide, a N,N-dialkyl (meth)acrylamide, a N,N-dialkylaminoalkyl (meth)acrylamide, a diacetone (meth)acrylamide, a N-vinylformamide, N-vinylacetamide and N-vinylpyrrolidone; aliphatic unsaturated hydrocarbons such as ethylene, propylene, isobutylene, isoprene and butadiene; styrene monomers such as styrene, α-methylstyrene, p-methoxystyrene, vinyltoluene, p-hydroxystyrene and p-acetoxystyrene; vinyl ester type monomers such as vinyl acetate and vinyl propionate; acrylonitrile; and glycidyl (meth)acrylate. These can be used singly or in combination of two or more.

The acid value of the high molecular weight polycarboxylic acid is 500 to 900 mgKOH/g and preferably 550 to 750 mgKOH/g. If the acid value of the polycarboxylic acid falls within the range of numerical values, the strength and rigidity of a cured product of the aqueous binder are improved and thickness recovery after unpacking the resultant inorganic-fiber heat-insulating sound-absorbing member from a compressed state and rigidity of the inorganic-fiber heat-insulating sound-absorbing member processed in the form of board are improved. In addition, heat insulating property, sound absorbability or workability at the time of construction such as self-standing property is excellent.

The weight average molecular weight of a high molecular weight polycarboxylic acid is 1000 to 20000, preferably 2000 to 15000 and more preferably 2000 to 10000. If the weight average molecular weight of a polycarboxylic acid falls within the range of numerical values, it is easy to control the fluidity of the aqueous binder to be one suitably applicable to an inorganic fiber and variation of the aqueous binder in the application amount can be suppressed. In producing an inorganic-fiber heat-insulating sound-absorbing member, an aqueous binder is often applied to a fiber immediately after fiberization in accordance with e.g., a centrifugation method, in a high temperature atmosphere of about 200 to 350° C. At this time, the water content in the aqueous binder can be satisfactorily vaporized.

The weight average molecular weight of a polycarboxylic acid is related to not only the fluidity of the aqueous binder but also a curing rate and a crosslink density after curing. Even if polycarboxylic acids have the same acid value, if the molecular weights differ, the curing rates of the aqueous binders and the strength of cured products of the aqueous binders change and the physical properties of the resultant inorganic-fiber heat-insulating sound-absorbing members also change. For example, as the weight average molecular weight of a polycarboxylic acid decreases, the curing rate of the aqueous binder increases; however, the cured product tends to be fragile. Depending upon the production conditions of a production line, there are cases where desired physical properties are not obtained. If the weight average molecular weight of a polycarboxylic acid falls within the above range, the fluidity of the aqueous binder and physical properties of the resultant inorganic-fiber heat-insulating sound-absorbing member can be optimally balanced.

The content (in terms of solid content) of a polycarboxylic acid in an aqueous binder is preferably 60 to 90 mass % and more preferably 65 to 88 mass % on a total mass basis of the aqueous binder in terms of solid content.

The aqueous binder comprises a crosslinking agent other than a polycarboxylic acid as mentioned above. The crosslinking agent includes at least one of a reactive compound having only at least one of an amino group and an imino group as a functional group reactive with the polycarboxylic acid or only a hydroxyl group. More specifically, a reactive compound without a hydroxyl group, the reactive compound having at least one of an amino group and an imino group or a reactive compound without an amino group and an imino group, the reactive compound having a hydroxyl group is included. Such a reactive compound (crosslinking agent) comprises a polyamine having a weight average molecular weight of 100 to 500 and an amine value of 1150 to 1650 mgKOH/g and a polyol having a weight average molecular weight of 90 to 250 and an alcohol valence of 3 or more, as essential components. The amine value refers to milligrams (mgKOH) of potassium hydroxide, which is equivalent to the amount of a hydrochloric acid solution required for neutralizing 1 g of polyamine.

As the crosslinking agent, the content of components except the essential components is not excluded; however, the total content of a polyamine and a polyol in the total amount of the crosslinking agent is preferably 90 mass % or more and further preferably 95 mass % or more and may be 100 mass %. The components except the essential components and that can be comprised as a crosslinking agent is essentially compounds comprising either one of an amino group or an imino group and a hydroxyl group.

Examples of the polyamine include an aliphatic polyamine, an alicyclic polyamine and an aromatic polyamine. Of them, an aliphatic polyamine is preferable in view of water solubility, and an aliphatic polyamine having an alkylene polyamine skeleton (preferably, linear skeleton) is preferable.

Examples of the polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, heptaethyleneoctamine, N-(3-aminopropyl)butane-1,4-diamine, N,N-di(3-aminopropyl)butane-1,4-diamine, bishexamethylene triamine, 1,2,3-propanetriamine and 1,1,4,4-butanetetramine.

The weight average molecular weight of a polyamine is 100 to 500 and preferably 150 to 400. Also in the case of the polyamine, similar to a polycarboxylic acid, the molecular weight thereof influences the fluidity and curing behavior of an aqueous binder. If the weight average molecular weight of the polyamine falls within the above range, the fluidity of the aqueous binder and the physical properties of the resultant inorganic-fiber heat-insulating sound-absorbing member can be optimally balanced.

The amine number of a polyamine is 1150 to 1650 mgKOH/g and more preferably 1200 to 1600 and further preferably 1200 to 1500. If the amine number falls within the range of the above numerical values, the polyamine quickly reacts with a polycarboxylic acid, raising the rate of increasing the molecular weight of a cured product of the aqueous binder and raising the strength of the cured product of the aqueous binder. In the same point of view, a polyamine is preferable to have at least three groups selected from the group consisting of amino groups and imino groups. The polyamine has no hydroxyl group.

The content of a polyamine in an aqueous binder (in terms of solid content) is preferably 0.2 to 5.0 mass % and preferably 0.3 to 4.0 mass % on a total mass basis in terms of solid content of the aqueous binder.

The polyol without an amino group and an imino group has a weight average molecular weight of 90 to 250 and an alcohol valence of 3 or more. If the alcohol valence is the lower limit or more, a crosslinking reaction is sufficiently improved, with the result that a dense crosslinking structure is obtained and the strength of a cured product of the aqueous binder increases.

As the polyol, a sugar alcohol having 3 to 8 carbon atoms is preferable. Examples of the sugar alcohol having 3 to 8 carbon atoms include glycerol, erythritol, pentaerythritol, threitol, arabinitol, xylitol, ribitol, iditol, galactitol, sorbitol, mannitol, volemitol, perseitol and D-erythro-D-galacto-octitol. Since the sugar alcohol has a molecular main chain, which is constituted of carbon-carbon bonds, the main chain of the molecule is not cleaved during a curing reaction of the aqueous binder. Because of this, the crosslinking degree of the aqueous binder sufficiently increases and the physical properties of a cured product of the aqueous binder can be ensured. In contrast, if e.g., an ether bond, an ester bond and an amide bond are present in the main chain of the molecule, the main chain of the molecule is cleaved to cause a transesterification reaction, with the result that the crosslinking degree of the binder is not increased despite the cure time and physical properties of the cured product of the binder may sometimes deteriorate.

The number of carbon atoms of the sugar alcohol having 3 to 8 carbon atoms is preferably 4 to 6 and more preferably 4 or 5. If the number of carbon atoms of the sugar alcohol falls within the above range, the crosslinking reaction is sufficiently improved, with the result that a dense crosslinking structure can be formed and the strength of a cured product of the aqueous binder increases.

The content (in terms of solid content) of a polyol in an aqueous binder is preferably 5 to 35 mass % and more preferably 8 to 30 mass % on a total mass basis in terms of solid content of the aqueous binder.

The effect of the present application can be efficiently exerted by obtaining the aqueous binder of the present invention by using a high-molecular weight polycarboxylic acid, a medium-molecular weight polyamine and a low-molecular weight polyol in combination; however, the weight average molecular weight of the polyol may not necessarily be lower than the weight average molecular weight of the polyamine.

The ratio of the total mole of the hydroxyl group, amino group and imino group in the crosslinking agent relative to the mole of the carboxy group in a polycarboxylic acid is 0.3 to 1.2 and preferably 0.5 to 1.0. If the molar ratio falls within the range of the numerical values, the polycarboxylic acid and the crosslinking agent easily form a crosslinking structure in just proportion, with the result that the strength of a cured product of the aqueous binder increases and the physical properties of the resultant inorganic-fiber heat-insulating sound-absorbing member become optimal.

The ratio of the total mole of the amino group and imino group in the crosslinking agent relative to the total mole of the hydroxyl group, amino group and imino group in the crosslinking agent is 0.01 to 0.2, preferably 0.01 to 0.15, more preferably 0.01 to 0.1 and further preferably 0.01 to 0.05. If the molar ratio falls within the range of the numerical values, a high molecular weight polycarboxylic acid and a crosslinking agent component, i.e., a polyamine and a polyol, immediately form a crosslinking structure. Since formation of an amide group and an imide group, which has an unfavorable effect upon water resistance, is suppressed, a change in the curing degree due to curing conditions is minor, with the result that the water resistance of the resultant inorganic-fiber heat-insulating sound-absorbing member is not impaired, and mechanical strength and the dimension of an insulating material can be ensured.

As described above, the aqueous binder obtained by blending a polycarboxylic acid and a crosslinking agent does not produce formaldehyde during curing and provides a cured product having excellent peel strength.

The aqueous binder may comprise a cure accelerator such as a reductive inorganic salt. Examples of the cure accelerator include a hypophosphite and a sulfite. These may be used singly or in combination of two or more. Examples of the hypophosphite include sodium hypophosphite, lithium hypophosphite, potassium hypophosphite, calcium hypophosphite, magnesium hypophosphite and strontium hypophosphite. Examples of the sulfite include lithium hydrogen sulfite, sodium hydrogen sulfite, potassium hydrogen sulfite, magnesium hydrogen sulfite, calcium hydrogen sulfite and ammonium hydrogen sulfite. Of them, lithium hydrogen sulfite, sodium hydrogen sulfite or ammonium hydrogen sulfite, which has a high content of a sulfite ion having a curing acceleration action, is preferable.

The content of the cure accelerator relative to the total (100 parts by mass) of a polycarboxylic acid and a crosslinking agent is preferably 0.1 to 10 parts by mass and more preferably 0.5 to 5 parts by mass in terms of solid content.

It is preferable that the aqueous binder comprises a silane coupling agent. The silane coupling agent acts at the interface between an inorganic fiber and a cured product of the aqueous binder, with the result that adhesion of the cured product of the aqueous binder to the inorganic fiber can be improved. Examples of the silane coupling agent include aminosilane coupling agents such as γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane and γ-(2-aminoethyl)aminopropylmethyldimethoxysilane; and epoxysilane coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropylmethyldimethoxysilane. These may be used singly or in combination of two or more.

The content of the silane coupling agent relative to the total of 100 parts by mass of a polycarboxylic acid and a crosslinking agent is preferably 0.1 to 2.0 parts by mass in terms of solid content.

To the aqueous binder, if necessary, for example, an inorganic sulfate (neutralizing agent) for neutralizing an alkaline component(s) eluted from a heavy oil dispersant as a dust-inhibiting agent, a colorant and an inorganic fiber such as glass, and other additives can be further added. As the inorganic sulfate, for example, ammonium sulfate can be mentioned.

The pH of the aqueous binder is preferably 6.0 to 8.0, more preferably 6.0 to 7.0 and further preferably 6.0 to 6.5. If the pH falls within the range of numerical values, corrosion of production equipment can be suppressed and wastewater can be easily treated, with the result that maintenance cost can be reduced. It is preferable that the pH is adjusted by use of a volatile basic compound. Examples of the volatile basic compound include ammonia water and an amine. In consideration of odor generating during curing, ammonia water is preferable.

The aqueous binder can be produced, for example, by the following method. More specifically, the above polycarboxylic acid and crosslinking agent, and, if necessary, a cure accelerator, a silane coupling agent, a heavy oil dispersant in water and other additives are added in a tank equipped with a stirrer such as a dissolver and then just mixed.

As the form of the aqueous binder, an emulsion, a colloidal dispersion and a water soluble composition are mentioned. Any form may be employed. The emulsion herein refers to an emulsion obtained by using an emulsifier, for example, a surfactant, which is different from a resin component (high molecular weight polycarboxylic acid) comprised in the aqueous binder. The colloidal dispersion refers to a dispersion obtained by dispersing a resin component in water with the help of a functional group comprised in the resin component. Generally, both have milk-white color appearance. In contrast, a water soluble composition refers to a composition obtained by dissolving a resin component in water and having transparent or nearly transparent appearance.

As the form of the aqueous binder, as will be described below, a water soluble composition is advantageous over an emulsion or a colloidal dispersion, since process management is easy. More specifically, in the emulsion and colloidal dispersion, the resin component (e.g., a high molecular weight polycarboxylic acid) dispersed therein is less soluble in water and less swellable and easily forms a film when water serving as a medium volatilizes. If the resin component in the aqueous binder forms a film before curing, the fluidity of the aqueous binder in the surface of an inorganic fiber tends to be impaired, with the result that an inorganic-fiber heat-insulating sound-absorbing member to which the aqueous binder is applied in a homogeneous amount cannot be obtained. In addition to this, the number of portions at which inorganic fibers are not mutually bound with the aqueous binder increases, with the result that it sometimes becomes difficult to keep the shape as a product. Also in the colloidal dispersion and emulsion, once a film is formed as a result of volatilization of water serving as a medium, the film rarely returns to the aqueous material. If the aqueous binder attaches to e.g., production equipment, complicated work is required for washing, with the result that productivity tends to decrease.

In contrast, if the aqueous binder is a water soluble composition, even if water gradually volatiles from the aqueous binder, a film is not immediately formed. Thus, the aqueous binder is free from the above problem. Accordingly, it is preferable that the aqueous binder is prepared as a water soluble composition.

Although the emulsion or colloidal dispersion has the aforementioned problems, the emulsion or colloidal dispersion can be used in practice without problems by using it under humidified conditions or controlling the water content. For the reason, which one of an emulsion, a colloidal dispersion and a water soluble composition should be selected as the form of the aqueous binder may be appropriately determined in accordance with use environment of an aqueous binder.

The solid content of the aqueous binder is preferably 5 to 40 mass % and more preferably 10 to 30 mass %. If the solid content is set to be 5 mass % or more, the amount of water is proper, with the result that excessively much time is not required for a curing step and good productivity can be maintained. If the solid content is set to be 40 mass % or less, the fluidity of the aqueous binder can be prevented from decreasing. The solid content herein refers to a component, which does not vaporize when the aqueous binder is heated at 1 atm and a temperature from room temperature (about 23° C.) or more and 100° C. or less. Note that, it is preferable that the component (volatile component) except the solid content is water.

The inorganic-fiber heat-insulating sound-absorbing member according to the embodiment has an inorganic fiber and a cured product of an aqueous binder as mentioned above for fixing (keeping) the inorganic fiber. More specifically, the inorganic-fiber heat-insulating sound-absorbing member can be obtained by applying the aqueous binder to the inorganic fiber and curing the aqueous binder by heating to mold.

As the density of the inorganic-fiber heat-insulating sound-absorbing member, a density usually used for a heat insulating materials and sound absorbing materials may be employed and is preferably 5 to 300 kg/m³.

The inorganic-fiber heat-insulating sound-absorbing member, can be produced, for example, as follows. More specifically, first, a molten inorganic raw material is fiberized by a fiberizing device. Immediately after that, an aqueous binder as mentioned above is applied to the inorganic fiber. Subsequently, the inorganic fibers to which the aqueous binder is applied are piled up on a perforated conveyor to form a bulky intermediary body of the inorganic-fiber heat-insulating sound-absorbing member and fed to e.g., a pair of upper and lower perforated conveyors providing a gap for obtaining a desired thickness. The intermediary body is heated while applying pressure to cure the aqueous binder. In this manner, the inorganic-fiber heat-insulating sound-absorbing member is formed. If necessary, the inorganic-fiber heat-insulating sound-absorbing member is coated with e.g., a surface covering material and cut into pieces having a desired width and length.

As the inorganic fiber, e.g., glass wool and rock wool, usually used in heat-insulating sound-absorbing materials can be used. As a method for fiberizing an inorganic fiber, various methods such as a flame method, a blowing-off method and a centrifugation method (also called as a rotary method) can be used. If the inorganic fiber is glass wool, it is preferable that a centrifugation method is employed.

As the timing at which an aqueous binder is applied to an inorganic fiber, any time after fiberization is acceptable. In order to efficiently apply the aqueous binder, applying immediately after fiberization is preferable for the application.

As a method for applying an aqueous binder to an inorganic fiber, a coating or spray method using e.g., a spray device, is mentioned. The amount of an aqueous binder applied is controlled in the same manner as in that for a conventional binder containing no water repellent. The amount of an aqueous binder applied, which varies depending upon the density and use of an inorganic-fiber heat-insulating sound-absorbing member, is preferably 0.5 to 15 mass % and more preferably 0.5 to 9 mass % in terms of solid content, based on the mass of the inorganic-fiber heat-insulating sound-absorbing member to which the aqueous binder was applied.

The inorganic fibers to which an aqueous binder is already applied by the above step are piled up on a perforated conveyor to obtain a bulky inorganic fiber intermediary body. Herein, it is preferable that when the inorganic fibers are piled up on the perforated conveyor, the fibers are vacuumed up by a suction device from the side of the surface of the perforated conveyor opposite to the surface on which the inorganic fibers are piled up.

As a method for heating an aqueous binder, for example, heating in a hot-air oven is mentioned. The heating temperature of the hot-air oven can be, for example, 200 to 350° C. The heat curing time can be appropriately controlled within the range of 30 seconds to 10 minutes depending upon the density and thickness of an inorganic-fiber heat-insulating sound-absorbing member.

An inorganic-fiber heat-insulating sound-absorbing member may be used as it is or coated with a surface covering material and put in use. As the surface covering material, paper, a synthetic resin film, a metal foil film, a nonwoven fabric, a woven fabric or a combination of these can be used.

The inorganic-fiber heat-insulating sound-absorbing member obtained in this manner has excellent peel strength. In addition, the aqueous binder does not release formaldehyde during thermal curing and thus reduces an environmental load compared to a conventional phenol/fonnaldehyde based binder.

In the above, the preferred embodiment of the present invention has been specifically described; however, the present invention is not limited to the above embodiment and can be modified in various ways.

There invention will be more specifically described by way of Examples below; however, the present invention is not limited to the following Examples.

Example 1

A polyacrylic acid (weight average molecular weight 12000, acid value 716 mgKOH/g), which was obtained by radical polymerization using sodium hypophosphite as a chain transfer agent, was dissolved with water to obtain a resin solution (solid content 46%). One hundred parts by mass in terms of solid content of the resin solution, 0.50 parts by mass in terms of solid content of triethylenetetramine (amine value 1450 mgKOH/g), 38.06 parts by mass in terms of solid content of erythritol and 4.0 parts by mass of sodium hypophosphite serving as a cure accelerator were mixed and the pH of the mixture was adjusted to be pH6.5 with a 25% ammonia water to obtain a water soluble composition. Further, 0.3 parts by mass of γ-aminopropyltriethoxysilane was added and the mixture was stirred. Thereafter, the mixture was diluted with water so as to obtain a solid content of 15%. Five parts by mass of a heavy oil dispersant in water having a solid content of 40% and 8.0 parts by mass of ammonium sulfate were added to obtain an aqueous binder. The ratio of the total mole of a hydroxyl group, an amino group and an imino group relative to the total mole of a carboxy group was 0.99. The ratio of the total mole of an amino group and an imino group relative to the total mole of a hydroxyl group, an amino group and an imino group was 0.01.

Example 2

An aqueous binder was obtained in the same manner as in Example 1 except that 2.27 parts by mass in terms of solid content of heptaethylene octamine (amine value 1200 mgKOH/g) and 12.27 parts by mass in terms of solid content of glycerol were used. The ratio of the total mole of a hydroxyl group, an amino group and an imino group relative to the total mole of a carboxy group was 0.35. The ratio of the total mole of an amino group and an imino group relative to the total mole of a hydroxyl group, an amino group and an imino group was 0.10.

Example 3

A polyacrylic acid (acid value 660 mgKOH/g, weight average molecular weight 7000), which was obtained by radical polymerization using sodium hypophosphite as a chain transfer agent, was dissolved with water to obtain a resin solution (solid content 50%/). One hundred parts by mass in terms of solid content of the resin solution, 1.38 parts by mass in terms of solid content of the heptaethylene octamine (amine value 1200 mgKOH/g), 17.17 parts by mass in terms of solid content of the xylitol and 2.0 parts by mass of the sodium hypophosphite serving as a cure accelerator were mixed and the pH of the mixture was adjusted to be pH6.5 with a 25% ammonia water to obtain a water soluble composition. Further, 0.3 parts by mass of γ-aminopropyltriethoxysilane was added and the mixture was stirred. Thereafter, the mixture was diluted with water so as to obtain a solid content of 15%. Five parts by mass of a heavy oil dispersant in water having a solid content of 40% and 8.0 parts by mass of ammonium sulfate were added to obtain an aqueous binder. The ratio of the total mole of a hydroxyl group, an amino group and an imino group relative to the total mole of a carboxy group was 0.50. The ratio of the total mole of an amino group and an imino group relative to the total mole of a hydroxyl group, an amino group and an imino group was 0.05.

Example 4

An aqueous binder was obtained in the same manner as in Example 3 except that 5.68 parts by mass in terms of solid content of triethylenetetramine (amine value 1450 mgKOH/g) and 37.50 parts by mass in terms of solid content of sorbitol were used. The ratio of the total mole of a hydroxyl group, an amino group and an imino group relative to the total mole of a carboxy group was 1.00. The ratio of the total mole of an amino group and an imino group relative to the total mole of a hydroxyl group, an amino group and an imino group was 0.125.

Comparative Example 1

A binder was obtained in the same manner as in Example 1 except that triethylenetetramine was not added and 38.80 parts by mass in terms of solid content of the erythritol was used. The ratio of mole of a hydroxyl group relative to the total mole of a carboxy group was 1.00.

Comparative Example 2

A binder was obtained in the same manner as in Example 1 except that 0.72 parts by mass in terms of solid content of 1,6-hexane diamine (amine value 966 mgKOH/g) and 39.13 parts by mass in terms of solid content of glycerol were used. The ratio of the total mole of a hydroxyl group, an amino group and an imino group relative to the total mole of a carboxy group was 1.01. The ratio of the total mole of an amino group and an imino group relative to the total mole of a hydroxyl group, an amino group and an imino group was 0.01.

Comparative Example 3

A binder was obtained in the same manner as in Example 1 except that 0.65 parts by mass in terms of solid content of triethylenetetramine and 49.95 parts by mass in terms of solid content of the erythritol were used. The ratio of the total mole of a hydroxyl group, an amino group and an imino group relative to the total mole of a carboxy group was 1.30. The ratio of the total mole of an amino group and an imino group relative to the total mole of a hydroxyl group, an amino group and an imino group was 0.01.

Comparative Example 4

A binder was obtained in the same manner as in Example 1 except that 13.64 parts by mass in terms of solid content of the triethylenetetramine and 31.22 parts by mass in terms of solid content of the erythritol were used. The ratio of the total mole of a hydroxyl group, an amino group and an imino group relative to the total mole of a carboxy group was 1.08. The ratio of the total mole of an amino group and an imino group relative to the total mole of a hydroxyl group, an amino group and an imino group was 0.26.

[Evaluation on Compressive Strength]

To glass fibers fiberized by a centrifugation method, the binders of Examples and Comparative Examples were individually applied by a spray so as to obtain a predetermined application amount. The glass fibers were each individually piled up on a perforated conveyor while vacuuming by a suction device to obtain intermediary bodies of inorganic-fiber heat-insulating sound-absorbing members. The intermediary bodies were each heated in hot air of 260° C. for 5 minutes to cure the binder to obtain inorganic-fiber heat-insulating sound-absorbing members (glass wool board) having a density of 24 kg/m³, a length of 1350 mm, a width of 430 mm, a thickness of 80 mm and a binder application amount of 8.0%. Measurement of 10/o compressive load was carried out in the thickness direction of the glass wool boards obtained at a rate of 1 m/minute. The results are shown in Table 1 and Table 2. Note that, in the glass wool board using the binder of Comparative Example 2, stain due to binder adhesion and deposition of inorganic fibers were frequently observed on the perforated conveyor on which the intermediary body of the inorganic-fiber heat-insulating sound-absorbing member is formed.

[Evaluation on Durability]

From each of the glass wool boards prepared as mentioned above, test pieces of 300 mm-squares having a thickness of 80 mm were cut out. After the test pieces were allowed to stand still in high temperature and high pressure vapor (temperature 105° C., pressure 35 kPa) for one hour, difference in thickness was determined. A change rate relative to the initial thickness was obtained. The results are shown in Table 1 and Table 2.

[Peel Strength]

From each of the glass wool boards prepared as mentioned above, test pieces of 100 mm-squares having a thickness of 80 mm were cut out. Two jigs for measuring peel strength, which was each a 100 mm-square board 2 mm in thickness, made of aluminum and having a protrusion of 30 mm in length at the center of one of the surfaces, were prepared. To the both surfaces of each of the test pieces, the surfaces of the peel-strength measurement jigs having no protrusion were separately attached with an adhesive. The two peel-strength measurement jigs were pulled in mutually opposite directions along the thickness direction of the test piece at a rate of 1 m/minute (peel rate). The load at the time when a test piece was broken was measured to obtain a peel strength (kg/m²). The results are shown in Table 1 and Table 2.

TABLE 1 Example Example Example Example 1 2 3 4 10% Compressive 90.5 89.4 89.8 90.1 strength (Kg/m²) Durability (%) 3.1 4.5 4.2 3.7 Peel strength (Kg/m²) 1.54 1.13 1.46 1.27

TABLE 2 Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 10% 72.4 81.0 79.4 84.2 Compressive strength (Kg/m²) Durability 4.6 5.2 5.7 6.4 (%) Peel strength 0.72 0.84 0.98 0.86 (Kg/m²)

As is shown in Tables 1 and 2, the inorganic-fiber heat-insulating sound-absorbing members using the aqueous binder of the present invention have a high peel strength and excellent values with respect to compressive strength and durability, which are known as measures for evaluating the quality of inorganic-fiber heat-insulating sound-absorbing members, and thus, can be more suitably used as an inorganic-fiber heat-insulating sound-absorbing member. 

What is claimed is:
 1. An aqueous binder for an inorganic-fiber heat-insulating sound-absorbing member, comprising a polycarboxylic acid and a crosslinking agent for the polycarboxylic acid, wherein the polycarboxylic acid comprises a polycarboxylic acid having a weight average molecular weight of 1000 to 20000 and an acid value of 500 to 900 mgKOH/g, the crosslinking agent comprises at least a polyamine without a hydroxyl group, the polyamine having at least one of an amino group and an imino group and having a weight average molecular weight of 100 to 500 and an amine value of 1150 to 1650 mgKOH/g, and a polyol without an amino group and an imino group, the polyol having a hydroxyl group and having a weight average molecular weight of 90 to 250 and an alcohol valence of 3 or more, a ratio of the total mole of the hydroxyl group, amino group and imino group in the crosslinking agent relative to the mole of the carboxyl group in the polycarboxylic acid is 0.3 to 1.2, and a ratio of the total mole of the amino group and imino group in the crosslinking agent relative to the total mole of the hydroxyl group, amino group and imino group in the crosslinking agent is 0.01 to 0.2.
 2. The aqueous binder according to claim 1, wherein the polycarboxylic acid comprises as a monomer unit an ethylenically unsaturated monomer having a carboxy group.
 3. The aqueous binder according to claim 1 or 2, wherein the polyol is a sugar alcohol having 3 to 8 carbon atoms.
 4. The aqueous binder according to claim 1 or 2, wherein the polyamine is an aliphatic polyamine having an alkylene polyamine skeleton.
 5. The aqueous binder according to claim 1 or 2, further comprising at least one selected from the group consisting of a cure accelerator, a silane coupling agent, a dust-inhibiting agent, a neutralizer and a colorant.
 6. An inorganic-fiber heat-insulating sound-absorbing member comprising an inorganic fiber and a cured product of the aqueous binder according to claim 1 or 2 for fixing the inorganic fiber. 